Integrator's note on the 3RT1035-3AC20
The Siemens 3RT1035-3AC20 is a SIRIUS power contactor in size S2, rated 22 kW at 500 V AC-3 and 18.5 kW at 400 V AC-2. That AC-3 figure governs motor switching up to that load — the contactor is sized for a 22 kW induction motor on a 500 V line, or 18.5 kW at 400 V. The 55 mm width and 115 mm depth fit a standard DIN-rail enclosure; screw terminals accept 2x (0.75... 25 mm²) stranded on the main circuit. IP20 on the front, IP00 at the terminals — the terminal area must be inside the panel, not exposed. Side-by-side mounting is allowed, so no derating for zero-gap spacing in a multi-contactor group.
The screw-type terminals on the main circuit accept 2x (0.75... 25 mm²) stranded or 2x (0.25... 2.5 mm²) solid — plan ferrule sizing for the stranded range. Coil terminals are 24 V at 50/60 Hz, so the control transformer must match that voltage.
Switching performance and thermal limits
Maximum operating rate varies by duty: 1 200 cycles/hour in AC-1 (resistive), 1 000 in AC-3 (motor), 600 in AC-2, and 300 in AC-4 (plugging/inching). The AC-4 limit is the binding constraint for reversing or jogging applications — plan the control sequence to stay under 300 ops/h. Storage temperature spans –55 to +80 °C, operating –25 to +60 °C — the storage range is wider because the contactor is not under load.